Starting device for compressors



June 3, 1930. c, w. METzGA R 1,761,578

STARTING DEVICE FOR COMPRESSORS Filed July 17. 1928 2 Sheets-Sheet l mINVENTOR. heal rllZfMegyae 5p ATTORNEY.

June 3, 1930, c. w. METZGAR STARTING DEVICE FOR COMPRESSORS Filed July17, 1928 2 Sheets-Sheet 2 6 (/2 1 11 T V 10- 03 l 6' 0r 3 HIS ATTORNEY,

- refer to similar parts,

Patented June 3, 1930 UNITED STATES,

PATENT OFFICE,

CHESTER W. METZGAR, OF, EASTON, PENNSYLVANIA, ASSIGNOR TO INGERSOLL-RANDCOMPANY, OF JERSEY CITY, N JERSEY, A CORPORATION OF NEW JERSEY STARTINGDEVICE FOR COMPRESSORS Application filed July 17,

This invention relates to compressors, but more particularly to a deviceadapted to be connected to the unloading control mechanism and themeans, such as a switch, whereby the current supply to the driving motorof the compressor is controlled.

One object of the invention is to prevent the starting of the drivingmotor until the compressor is fully unloaded.

Other objects will be in part obvious and in part pointed outhereinafter.

In the accompanying drawings illustrating a practical application oftheinvention and in which similar reference characters Figure 1 is anend elevation of the multicylinder compressor with its intercoolerhaving the invention applied thereto,

Figure 2 is an elevation of a detail partly in section illustrating theposition of the throttle valve to prevent closing of the startingswitch, v v m Figure 3 is a similar view showing the throttle valve in aposition to enable the starting switch to be closed,

Figure 4: is a transverse view taken through Figure 3 on the line 4-4looking in the direction indicated by the arrows, and Figure 5 is atransverse view taken through Figure 2 on the line 5 5 looking in thedirection indicated by the arrows.

Referring more particularly to the drawings, A designates generally acompressor, in this instance a compound compressor having a low pressurecylinder B and a high pressure cylinder C. An intercooler D is disposedon the cylinders 13 and C to convey fluid compressed by the cylinder Bto the cylinder C and to extract the heat of compression from such fluidin a well known manner.

Suitable and well known means are provided for reducing the capacity ofthe compressor cylinders B and C whenever the pressure in a storagereceiver (not shown) reaches a maximum value which it is desired tomaintain therein. These means in the present instance are illustrated assuitable clearance valves, only the casings E of which are shown toindicate the positions 1928. Serial No. 293,459.

which the clearance valves may occupy on the compressor cylinders.

The unloading devices or clearance valves E may be identical on bothcylinders and preferably one clearance valve of each cylinder is incommunication through suitable connections with a clearance valve of theothercylinder. This is accomplished in the case of the clearance valveson the adjacent or opposite sides of the cylinders B and C by means of apipe F having a branchG which leadsto a regulator H of the typedisclosed and described in United States Patent No. 1,430,578 grantedtoChester W. Metzgar, October 3, 1922. Reference may be had to theaforesaidpatent fora detail description of the regulator and only somuch, of the regulator will be described herein as is necessary todescribe the invention and its application.

In the case where additional clearance valves E are provided for thecylinders as for instance, the valve E on the outer or left hand side ofthe low pressure cylinder B as Figure 1 is viewed, such clearance valvesare also preferably connected in pairs or groups by means of a pipe Jhaving a branch K forming a connection between the pipe J and theregulator H.

Suitableunloadin means are also nois l.

vided for the intercooler D. This means comprises a casing L which maybe suitably secured to one end of the intercooler and has a passage 0 toafford communication between the interior of the intercooler D and theatmosphere. In the passage 0 is formed a valve seat P for a check valveQ which cooperates with the seat P for controlling communication betweenthe intercooler and the atmosphere.

Inorder to normally maintain the valve Q on its seat a spring R isdisposed be tween the valve and a cover plate S on the casing L toconstantly exert a slight pressure on the valve for maintaining it inthe closed position. Additional means are provided however, for exertinga pressure on the valve to maintain it closed during the normaloperation of the compressor and this means consists of a pipe T whichcom- H whenever pressure fiuid is admitted into the valve chamber U formaintaining the valve closed the pipe T is provided with a branch Xwhich is connected to the regulator H for supplying pressure fluidthereto for the purpose of maintaining the clearance valves E closed.

By referring to the aforesaid patent it will readily be seen thatwhenever the receiver pressure attains the maximum value at which theregulator H is adapted to operate, one clearance valve E of bothcylinders B and C will be simultaneously allowed to open and as thepressure in the storage receiver increases other valves connected inseries on both cylinders will also be opened,

' however, the unloading valve on the intercooler D will remain closed.

In accordance with the present invention a valve casing Y is interposedin the pipe T between the branch X and the drain tank V. In this casingY is disposed a throttle valve Z of the three-way type having ports I)and on diametrically opposite sides of the throttle valve Z to controlcommunica tion between the pipe T and the drain tank V. The throttlevalve Z is further provided with a port (I disposed at right angles tothe ports I) and c for establishing communication between the pipe T andan exhaust port 6 in the valve casing Y in the open position of thethrottle valve Z.

The throttle valve Z is of the type which is adapted to be manuallyoperated and accordingly has a stem 7 which extends beyond the confinesof the casing Y to receive '5: a lever 9 whereby the throttle valve Zmay be manipulated. The lever g carries a head it through which the stem7 extends and on the outer end of the head 72 is a cam surface jpreferably so formed that its lowermost portion is will lieapproximately in the. horizontal plane of the throttle valve Z when thesaid throttle valve is in a position to exhaust the pressure fluid fromthe various unloading valves. The high portion .0 of the cam surfacepreferably lies at right angles to the low portion is so that only aquarter turn of the throttle valve Z will be necessary to carry the highportion 0 into the horizontal plane of the throttle valve Z.

Disposed adjacent to the throttle valve head h is a bracket p which maybe secured to. the pipe T by means of a suitable clamp g and bolts 1*which serve to clamp the bracket 9) to the pipe T. The bracket 7) mayhowever be mounted in any other suitable manner and serves as a mountingfor a push button switch 8 of a well known type having movable contactst adapted to be pressed into engagement and held in engagement withstationary contacts a by means of a push button 4;. The push button r inthis instance is the starting button, and the function of the contacts 6and u is to close the circuit between leads an leading from the pushbutton switch 3 to magnetically actuated control switches (not shown)but which may be located at a point remote from the push button switchfor opening and closing the circuit of a motor not shown) whereby thecompressor is actuated.

Only a brief description of the push button switch 8 is considerednecessary since it is a well known device adapted for use such as thatdescribed. It may however be stated. that the switch has an additionalmovable contact a" and a cooperating stationary contact y from whichlead leads 2 to the main switches for again opening the main switches.The movable contact as in this instance also carries a push button 2which may be pressed by the operator to move the contact x against thecontact 1 and to hold said contact in engagement until the main switchesare again opened.

Both of the movable contacts t and to are provided with springs 3 sodisposed beneath the contacts as to exert a pressure to immediatelyrestore the contacts to their open position upon the release of pressureto the push buttons '0 and 2. The push buttons c and 2 are provided withstems 4 and 5 respectively which are guided by suitable apertures 6 inthe casing of the push button switch 8. The push button switch 8 is sodisposed with respect to the cam surface j that the stem 4 of the switchwill lie approximately in the horizontal plane of the throttle valve Zand will therefore be in coaxial alignment with a bore 7 in the bracketp. The bore 7 serves as a guide for a pin, 8 disposed slidably in saidbore and said pin is of such length that it may abut with one end thestem 4 of the push button '0 and extends with its other end to a pointnear the cam surface or, if desired, the end of the pin may come intodirect contact with the said cam surface.

The operation of the device is as follows: During the normal operationof the compressor the throttle valve Z occupies the position illustratedin Figure In this position the ports Z) and 0 of the throttle valve willafford communication between the opposite sections of the pipe T. Theexhaust port 0 will be closed. Pressure fluid may therefore flow fromthe drain tank V through the pipe T to the regulator H and thus also tothe valve chamber U to maintain the valve Q in its closed position. Atthe same time pressure fluid will flow through the branch X ofthe pipe Tto the regulator H and thence through the pipes i, F, K and J to theclearance valves E for maintaining sai d clearance valves closed.

As will be readily understood, while the clearance valves E and thevalve Q are closed the compressor cylinders B and C will operate attheir full capacities. The air compressed in the cylinder B will passthrough the intercooler D to the cylinder C where it will be compressedto a higher value and from thence will pass to the storage receiver.During such operation of the compressor the step-by-step unloading orthe complete unloading of the compressor cylinders will be controlled bythe regulator H.

Whenever it is desired, for well known reasons, to quickly unload boththe compressor cylinders B and C and the intercooler D the throttlevalve Z may be rotated to the open position, in other words to aposition in which the port Z) in the throttle valve is in registry withthe exhaust port 0 and the port d therefore in registry with the pipe T.The pressure'fiuid previously utilized for maintaining the clearancevalves E and the valve Q closed will then be exhausted to the atmosphereand any slight compression which may be created in the low pressurecylinder B will pass into the intercooler D and into the passage 0 whereit may unseat the valve Q, and escape to the atmosphere. The pressure ofthe air compressed in the low pressure cylinder B will however be of lowpressure since the spring R acting against the valve Q is preferablycapable of exerting a pressure of only a few pounds.

By rotating the throttle valve Z to its open position the low portion 70will lie in the plane of the pin 8 so that when it is again desired toresume operation of the compressor the contact t may be readily pressedinto engagement with the stationary contact a to close the circuitbetween the a receiver through the various pipes and the regulator H tothe clearance valves E into the valve chamber U for loading thecompressor cylinders and the intercooler.

As has been previously intimated, when the throttle valve Z is in itsopen position the low portion In of the cam surface will be in alignmentwith the pin 8 to enable the contact to be pressed into engagement withthe contact a. When the throttle valve Z occupies its other extremeposition or in other words, its closed position, the high portion 0 ofthe cam surface j will be carried to the position previously occupied bythe low portion is of the cam surface. WVith the high portion 0 thusdisposed the contact 25 will occupy its extreme outermost position andwill be held in that position by the high portion 0 of the cam surfacewhich will then bear against the end of the pin 8. With the high portion0 in this position the throttle valve Z will of course be in a positionto admit pressure fluid to the regulator H so that the compressor andthe intercooler will be fully loaded. If then it be desired to set thecompressor in operation. itwill be impossible to establish contactbetween the starting contacts t and it until the throttle valve hasagain been moved to its open position and the compressor motor willtherefore be protected against the effects of starting under a fullload.

I claim:

1. In a compressor, the combination of a cylinder and a pressureactuated unloading device for the cylinder, means for controlling thesupply of pressure fluid to the unloading device, a switch forcontrolling the current supply to a motor connected to actuate thecompressor, and means associated with the first said means and theswitch to enable the switch to be closed for starting the compressoronly when the first said means occupies a position in which thecompressor is entirely unloaded.

V 2. In a compressor, the combination of a cylinderand a pressureactuated unloading device for the cylinder, a valve controlling thesupply of pressure fluid to the unloading device, a cam carried by thevalve and rotatable therewith, a switch for controlling the currentsupply to a motor connected to drive the compressor, and meansinterposed between the cam and the switch to prevent closing of theswitch while the compressor is loaded. I

3. In a compressor, the combination of cylinders and an intercooler,pressure actuated unloading devices for the cylinders and theintercooler, means for conveying pressure fluid from a storage receiverto the unloading devices, a valve on said means to control the flow ofpressure fluid through said means, a cam carried by the valve androtatable therewith, a switch adjacent the cam for controlling thecurrent supply to a motor connected to drive the compressor, and a pininterposed between the switch and the cam to prevent closing of theswitch when the valve is in a position to admit pressure fluid to. theunloading devices.

4. In a compressor, the combination of cylinders and an intercooler,pressure actuated unloading devices for the cylinders and theintercooler, means for conveying pressure fluid from a storage receiverto the unloading devices, a rotatable valve for controlling the flow ofpressure fluid through said means, a cam rotatable with the Valve, :1switch for controlling the supply of current to a motor connected todrive the compressor, a bracket adjacent the cam and forming a mountingfor the switch, and a pin slidable in the bracket and interposed betweenthe switch and the cam to prevent closing 01": the switch while theValve occupies a position to admit pressure fluid to the unloading meansfor maintaining the cylinders and the intercooler loaded.

In testimony whereof I have signed this 15 specification.

CHESTER \V. METZGAR.

